Hindawi Publishing Corporation BioMed Research International Volume 2014, Article ID 819324, 12 pages http://dx.doi.org/10.1155/2014/819324

Review Article Advance of Molecular Technology and Targeted Imaging Agent in Imaging and Therapy

Zhi-Yi Chen,1 Yi-Xiang Wang,2 Yan Lin,1 Jin-Shan Zhang,3 Feng Yang,1 Qiu-Lan Zhou,1 and Yang-Ying Liao1

1 Department of Medicine, Laboratory of Ultrasound Molecular Imaging, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou 510150, China 2 Department of Imaging and Interventional , Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong 3 Department of , The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou 510150, China

Correspondence should be addressed to Zhi-Yi Chen; [email protected]

Received 27 October 2013; Revised 29 December 2013; Accepted 30 December 2013; Published 13 February 2014

Academic Editor: Weibo Cai

Copyright © 2014 Zhi-Yi Chen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Molecular imaging is an emerging field that integrates advanced imaging technology with cellular and . Itcan realize noninvasive and real time visualization, measurement of physiological or pathological process in the living organism at the cellular and molecular level, providing an effective method of information acquiring for diagnosis, therapy, and drug development and evaluating treatment of efficacy. Molecular imaging requires high resolution and high sensitive instruments and specific imaging agents that link the imaging signal with molecular event. Recently, the application of new emerging chemical technology and nanotechnology has stimulated the development of imaging agents. Nanoparticles modified with small molecule, peptide, antibody, and aptamer have been extensively applied for preclinical studies. Therapeutic drug or gene is incorporated into nanoparticles to construct multifunctional imaging agents which allow for theranostic applications. In this review, we will discuss the characteristics of molecular imaging, the novel imaging agent including targeted imaging agent and multifunctional imaging agent, as well as cite some examples of their application in molecular imaging and therapy.

1. Introduction and SPECT), ultrasound (US) imaging and magnetic reso- nance imaging (MRI) [9]. In the past two decades, imag- Molecular imaging is a rapidly developed multidiscipline ing instruments have grown exponentially. Improvement in which involves molecular biology, , computer, engi- instruments and iterative image reconstruction has resulted neering, and medicine [1]. It can realize noninvasive and real in high resolution images that reveal tiny lesion and realize time visualization, measurement of physiological or patho- accurate quantification of biological process. A parallel devel- logical process in the living organism at the cellular or molec- opment has been the preparation of imaging agents which ular level [2, 3]. And it also allows repeated studies in the same can bind their targets with high specificity and affinity10 [ ]. animal, thus making it possible to collect longitudinal data In this review, we will discuss the characteristics of molecular andreducethenumberofanimalsandcost[4]. Therefore, imaging, some novel imaging agents based on nanoparticles molecular imaging plays an important role in earlier detec- including targeted imaging agent and multifunctional imag- tion, accurate diagnosis, and drug development and discov- ing agents, and cite some examples of their application in ery [5–7]. Molecular imaging requires high resolution and molecular imaging and therapy. high sensitive instruments to detect specific imaging agents that link the imaging signal with molecular event [8]. There 2. Molecular Imaging Technology are five imaging modalities available for molecular imag- ing, including X-ray computed tomography imaging (CT), 2.1. Radionuclide Imaging. Radionuclide molecular imaging optical imaging (OI), radionuclide imaging (involving PET including PET and SPECT is the earliest and most mature 2 BioMed Research International molecular imaging technique. Due to its advantages of high sensitivity and quantifiability, radionuclide molecular imaging plays an important role in clinical and preclinical researches [11]. Over the past decade, with the progress of molecular biology and radiochemistry, a variety of tracer with high specificity and affinity appeared. A lot of preclinical and clinical studies have confirmed the feasibility of using radionuclide molecular imaging to detect tumor and predict response to therapy [12, 13].

2.1.1. PET. PET is the molecular imaging modality most extensively used in current clinic routine. It measures the sig- nal originated from the radioactive decay of neutron-defi- 11 15 18 131 cient radioisotopes (such as C, O, F, and I) that are intravenously injected into the body. These isotopes emit positrons which are ejected from the nucleus as a result of springless interactions with electrons in surrounding tissue. The positrons rapidly lose kinetic energy by spreading around thetissueandcollidewithanelectrontoformtwo511keV (a) (b) ∘ photons which are taking trajectory 180 apart, and this is an Figure 1: Dual-isotope SPECT/CT images of tumor-bearing mice. event known as annihilation [14]. A PET detector surround- (a) The mice were imaged 1 h after coinjection of 1.32 nmol 177 ing the subject is designed to detect the signal and convert Lu—DOTA—cRGDfK (yellow-green colormap) and 1.32 nmol 111 the resulting electrical signal into sinograms that are finally In—DOTA—cRADfK (blue-purple colormap); (b) the mice were 111 rebuilt into tomographic images. imaged 1 h after coinjection of 1.32 nmol In—DOTA—cRGDfK −11 −12 177 Because of its high sensitivity of 10 ∼10 mol/L, limit- (blue-purple colormap) and 1.32 nmol Lu—DOTA—cRADfK less depth of penetration, and quantitative capabilities, PET (yellow-green colormap). The white arrows indicate the locations becomes a powerful tool for clinical diagnosis and basic of tumor [23]. research including neurology, cardiology, and particularly oncology [15, 16]. In the clinic, PET is crucial for cancer detec- tionandstaging,aswellasevaluationofresponsetotherapy. less sensitive since the photons which are not traveling along A mass of radiotracer has been employed for cancer imaging, theaxisofthecollimatorarerejectedbythescanner.The 18 with F-FDGbeingthekeyone.Themaindisadvantageof spatial resolution (8–10 mm) of SPECT is lower than that PET is the lack of anatomical parameters to identify molecu- of clinical PET (5–7 mm) [20], but the spatial resolution of lar events with accurate correlation to anatomical findings, small animal SPECT (micro-SPECT) is higher than that of and this disadvantage has recently been compensated by PET due to the development of imaging equipment. Thus mergingthesedeviceswitheitherCTorMRI[17]. It is micro-SPECT is more available in preclinical investigations reported that whole-body PET/CT improves the accuracy including the transformation research and animal studies of cancer diagnosis and staging. With the widespread of such as oncology, neurology, cardiovascular disease, and drug instrument, PET/CT has become an important tool for pre- development [21, 22]. Additionally, since the radionuclides dicting therapeutic response, providing useful information commonly available for SPECT have longer half-life periods for the decision to stop ineffective treatment or switch to (ranging from a few hours to days), longitudinal studies can beperformed.Basedontheisotope-specificenergiesofthe a more efficient treatment. It is shown that up to 40% of 111 177 patients with cancer have changed the treatment because of emitted photons (e.g., [ In] indium: 171 and 245 keV; [ Lu] application of PET/CT [18]. Recently, Andrade et al. [19] lutetium: 202 and 307 keV), SPECT can distinguish different evaluated 40 patients with invasive ductal breast carcinomas radioisotopes, therefore making it possible to image different that received neoadjuvant chemotherapy by FDG-PET/CT. targets simultaneously. Hijnen et al. [23]tookadvantageof They found that the application of FDG-PET/CT after the this characteristic and devised a dual-isotope experiment second course of NAC could predict therapeutic response on a micro-SPECT system. In their study, they quantified in ductal breast carcinomas and potentially recognise the the biodistribution and tumor uptake of the angiogenesis nonresponding patients for whom ineffective chemotherapy tracer cRGD via SPECT (Figure 1). However, dual-tracer should be avoided. Other limitations of PET are their safety images can be severely distorted due to cross talk between profile and the requirement of cyclotron to produce radio- the two isotopes. Recently, Hapdey et al. [24]putforwarda pharmaceuticals. generalized spectral factor analysis (GSFA) method for solv- 99 123 ing this problem in simultaneous mTc/ I SPECT, which 99m 123 2.1.2. SPECT. Unlike PET, SPECT directly detects gamma- proved that simultaneous Tc/ Iimagingcanprovide ray photon emitted by the chosen radionuclide during their images of similar quantitative accuracy through GSFA as 99 123 decay. Compared with PET, SPECT is more affordable and when using sequential and scatter-free mTc/ Iimagingin extensively employed in the clinical routine, but it is generally brain SPECT. BioMed Research International 3

2.2. Magnetic Resonance Imaging. Magnetic resonance imag- nanoparticles for CT imaging at the cellular and molecular ing (MRI) is a highly versatile imaging modality [25]. During level have been successfully prepared. Li et al. [35] conjugated the past decades, improvement in instrument launched the 2-deoxy-D-glucose (2-DG) to a gold nanoparticle to prepare field of MRI into a new era of molecular imaging. The merits CT molecular imaging agent (AuNP-2-DG) which could be of MRI as an imaging modality for molecular imaging are rel- used for CT imaging to obtain high resolution anatomic atively high temporal and spatial resolution, excellent tissue structure and metabolic information of tumor. The results contrast and tissue penetration, no ionizing radiation, non- of in vitro experiments proved that AuNP-2-DG could be invasiveness for serial studies, and simultaneous acquisition usedasafunctionalCTcontrastagent.However,thoughthe of anatomical structure and physiological function [26]. Nev- findings from these CT molecular imaging experiments show ertheless, molecular MRI is limited by its relatively low sen- attractive prospect, further study is required to explore the sitivity, and this requires the introduction of imaging agent feasibility of CT molecular imaging. and development of powerful signal amplification strategies. Imaging agent design is hence an important topic in molec- 2.4. Optical Imaging. Optical molecular imaging technology ular MRI. Currently, the MR imaging agents are mainly is an emerging technology, based on genomics, proteomics, divided into two kinds: ferromagnetism contrast agents and and modern optical technology. At present, the most widely paramagnetic contrast agents. The former is considered as negative contrast agents which mainly reduce the signal in used optical molecular imaging modalities in vivo include T2-weighted images, while the latter is referred to as positive bioluminescence imaging (BLI) and imaging. As contrast agents that increase the signal in T1-weighted images. optical imaging is performed through the use of light, thus it The most representative negative contrast agents are super- is considered as relatively safe. And due to their advantages of paramagnetic iron oxide (SPIO) and ultrasmall superpara- high sensitivity and low cost, optical imaging plays a central magnetic iron oxide (USPIO), and typical positive contrast role in the investigation of tumor occurrence, progressions agents are small molecular weight compounds involving a and relevant drug development [36, 37]. The main disadvan- single Lanthanide chelate as signal producing element (e.g., tages of optical imaging are that the depth of penetration gadolinium-DTPA). To date, there are numerous examples of is limited as the energy of photons is low, thereby making MR molecular imaging which have confirmed the potential it nearly impossible to image deep tissues in large subjects. of this technology. Rapley et al. [27] demonstrated that the Due to the small size of experimental animals, the depth of penetration is not a problem for them. Therefore, optical application of antibody-SPIO complex and MRI was a feasible imaging is widely used for preclinical research. method for detecting and measuring nucleosome concentra- tion in vitro, which was expected to become a diagnostic, BLI is taking advantage of the light produced by the prognostic, and predictive tool in the management of cancer. enzymatic oxidation reaction of luciferase and its substrate. Recently, Debergh et al. [28] showed that the application The luciferase is usually generated from the reporter gene. As 𝛼 𝛽 opposed to fluorescence imaging, the light source of BLIis of a small monogadolinated tracer targeting v 3 integrin and MR molecular imaging was a promising strategy for from interior. And since tissue do not produce endogenous evaluation of colorectal cancers associated angiogenesis. bioluminescence, the sensitivity and signal to background is better than fluorescence imaging. BLI is widely used to observe the biological processes in vivo like disease progres- 2.3. X-Ray Computed Tomography Imaging. CT imaging sion, certain gene expression, tumor growth, and metastasis technologies have undergone a very fast development in and evaluate the effect of certain treatments. For example, the last years. High resolution small animal CT (micro- Niu et al. [38] introduced a caspase-3 specific cyclic firefly CT) has transformed CT imaging from organ, tissue to luciferase reporter gene (pcFluc-DEVD) into UM-SCC-22B molecular level, which is playing an increasingly important and 4T1 cells then induced apoptosis of the cells by different role in preclinical researches [29, 30]. The main advantages concentrations of doxorubicin and evaluated the effect by of CT are high spatial resolution (micro-CT is 0.02∼0.30 mm; BLI. The results exhibited that BLI intensity was increased clinical CT is 0.5∼2.0 mm), fast acquisition time, relative as early as 24 h after treatment and achieved a maximum at simplicity, availability, excellent hard-tissue imaging. Due to around day 12, which indicated that BLI with pcFluc-DEVD limitations like ionizing radiation, limited soft tissue reso- as a reporter gene can help to observe the kinetics of the −2 −3 lution, and poor sensitivity (10 ∼10 mol/L), CT is always apoptotic process in a real-time manner (Figure 3). combined with other imaging modalities such as SPECT, Fluorescence imaging is a versatile technique with a num- PET to provide anatomical parameters for the biochemical ber of strengths such as relative low cost and multiplexed and physiological findings31 [ ]. Recently, the development of imaging. As light is absorbed by hemoglobin and other CT contrast agents has brought new hope for CT molecular molecules, the depth of penetration is limited (usually <1cm). imaging [32]. For example, Hyafil et al. [33]reportedcellular Hence, fluorescence imaging is mainly used in animal imaging of macrophage in the atherosclerotic plaque in a rab- researches. Atreya et al. [39] took advantage of the feature that 𝛼 𝛽 bit model through CT with iodinated nanoparticles (N1177) integrin v 3 and vascular endothelial growth factor receptor (Figure 2). Pan et al. [34] found that polymeric nanoparticles (VEGFR) are overexpressed in tumor; they used the integrin 𝛼 𝛽 contrast agents which were comprised of organometallics v 3 fluorescent probe to detect the tumor angiogenesis in or radiopaque organically soluble elements could further nude mice. The result showed there were strong fluorescence 𝛼 𝛽 improve the imaging sensitivity for CT. Also, targeted gold signals for v 3 in vivo via a fluorescent scanner, which 4 BioMed Research International

320

143

−35

(a) (b)

155

107 59

(c) (d)

Figure 2: CT molecular imaging based on iodinated nanoparticles (N1177). The kinetics and distribution of iodinated nanoparticles (N1177) in the atherosclerotic rabbit model were displayed by CT imaging. (a) 5 min after intravenous injection of N1177, CT image display aorta, and vena cava (red arrow) with a noticeable signal; (b) the reconstruction of three-dimensional CT imaging; (c) 2 h after intravenous injection of N1177, a strong signal was displayed in the spleen (∗); (d) use of color scale to reconstruct three-dimensional CT angiograms of CT scan. (adopted from Hyafil et al. [33]).

5 ×10 molecular imaging has many advantages including good 4 temporal resolution, quantitative data, real-time practice, noninvasiveness, relatively inexpensive cost, and no ionizing 3 radiation. In addition, it is a unique modality in some sense that it can be employed for diagnostic imaging and as a 2 therapeutic tool [42, 43]. Mancini et al. [44]provedthat the use of ultrasound molecular imaging with microbubble 1 targeting VEGFR-2 might be a valuable method for nonin- vasively detecting and quantifying of VEGFR-2 expression 2 0 hr 24 hr 48 hr 96 hr (p/s/cm /sr) in thyroid cancer in mice, and it is also a useful tool for differentiating benign from malignant thyroid nodules. Figure 3: After doxorubicin treatment (5 mg/kg), bioluminescence Besides, for diagnostic purposes, molecular ultrasound imaging was performed to observe caspase activation in 22B- pcFluc-DEVD (adopted from Niu et al. [38]). imaging can also be applied for theranostic purposes. This is mainly achieved by loading gene or drug onto microbub- ble. The interaction between ultrasound and microbubble results in stable and inertial cavitation, which can tran- indicated angiogenesis increased in the cancer tissue. Also, siently increase vascular and cellular membrane permeability, they proved that the targeted visualization of VEGF could thereby potentially augments the extravasation and/or take be achieved via a fluorescent-labeled antibody against the up of drugs or genes loaded on microbubble. Li et al. [45]pre- VEGFR (Figure 4). pared a novel microbubble carrying 10-HCPT, and they dem- onstrated that the injection of 10-HCPT loaded microbubble 2.5. Ultrasound Molecular Imaging. With the use of ultra- and exposure to ultrasound could increase the drug concen- sound , ultrasound imaging enables specific tration in tumor remarkably, leading to a significant increase and sensitive depiction of molecular targets [40, 41]. Com- in tumor inhibition rate (70.6%) compared with 10-HCPT pared with other molecular imaging modalities, ultrasound loaded microbubble alone (47.8%) as well as commercial BioMed Research International 5

(a) (b) 𝛼 𝛽 Figure 4: Nude mice was injected with SW620 CRC cells then administered intravenously with integrin v 3 fluorescent probe after the 𝛼 𝛽 formation of intestinal tumor. Via a fluorescent scanner, the targeted fluorescence signals for v 3 were observed in vivo (a). A fluorescent- labeled antibody against the VEGFR was injected intravenously, and fluorescence was detected using a multispectral in vivo imaging system (b) (adopted from Atreya et al. [39]).

HCPT injection (49.4%). Our studies have confirmed that the 100%,85%,and90%,respectively.Thepositivepredictive combination of ultrasound and microbubble could signifi- value was 77%, while the negative predictive value was 100%. cantly increase the transfection efficacy46 [ ]. MRIshowsobviousadvantagesoverCTincludingexcel- lent soft tissue contrast, high spatial resolution, and no ion- 2.6. Multimodality Imaging. Among all molecular imaging izing radiation; thus studies of PET/MRI become the focus techniques, every molecular imaging technique has its advan- of concern and have achieved initial progress. Lee et al. [54] tages and disadvantages. No single one is perfect and enough usedPET/MRItoevaluatethepresenceofmonocytesinnon- to provide comprehensive information for disease diagnosis ischemic remote zone after myocardial infarction, which [47]. In general, CT, MRI, and US are anatomic imaging proved that inflammatory cells of infarct zone and distant methods but they have low sensitivity. Radionuclide imaging noninfarcted area could be observed by PET/MRI images. and optical imaging are functional imaging techniques, while Recently, PET/MRI has been applied to clinic. Kjær et al. they suffer from low resolution, which often lack structural [55] performed a PET/MRI examination on a female patient parameter. The combination of different molecular imaging with cervical cancer for restaging following radiotherapy techniques, namely, multimodality imaging, can provide syn- and compared the results with PET/CT, which showed that ergistic advantages over any modality alone and compensate PET/MRI performed well compared to PET/CT.It had a more forthedisadvantagesofeachimagingsystemwhiletaking precise definition of the primary tumor (Figure 5). However, advantage of their individual strengths, which has become the PET with MRI in a single gantry which is dedicated to developmental trend of modern medical image now [48–51]. simultaneous PET/MRI is technically more challenging. Multimodality imaging such as PET/SPECT, PET/CT, and In addition to the combination of PET and CT or MRI, PET/MRI can be used to obtain anatomical and molecular other multimodality imaging methods have been reported, information while providing enough information for clinical such as OI/US, OI/CT, OI/MRI, and US/MRI [56–58]. OI is diagnosis [52]. For example, the combination of PET and CT a versatile technique in preclinical research as it possesses the can produce coregistered data providing regions of increased 18 advantages of high specificity and sensitivity, low cost, rela- F-FDGaccumulationonthePETimagewithprecise tively high-flux, and convenience. Ultrasound, on the other correlation to anatomical findings’ locations on the CT scan, hand, has strength of high resolution. The strengths of these thus the specificity and sensitivity of PET in detecting lesion imaging techniques are complementary. The combination of are enhanced, so as the accuracy in delineating target volume. them, which takes advantage of high sensitivity of optical Abgral et al. [53] conducted a study that included 91 patients imaging and high resolution of ultrasound, may produce syn- who once had HN cancer but were cured and without ergistic effect and provide images with good spatial and tem- any clinical evidence of recurrence to assess the diagnostic poral resolution. Lately, Li et al. [56] designed a system which 18 capabilities of F-FDG PET/CT in these patients. The results integrated imaging and 3D continuous tran- 18 showed that the sensitivity, specificity, and accuracy of F- sillumination fluorescence tomography. They evaluated the FDG PET/CT for the diagnosis of HN cancer recurrence were feasibility and performance of the system by using phantoms 6 BioMed Research International

CT sag FDG/PET PET/CT

T2 sag (MR) FDG/PET PET/MR

18 Figure 5: 31-year-old female patient with cervical cancer had an F FDG-PET/CT and PET/MRI examination for restaging following radiotherapy. PET/CT showed the primary tumour in the cervix behind the urine bladder and a lymph node in the pelvis, both indicated with arrows. PET/MR exhibited the same findings but with a more precise definition of the primary tumor (adopted from Kjær etal.[55]). and atherosclerosis disease mouse model. Results proved that imaging agents to recognise specific pathological tissues ultrasound structural images could improve the quality of the [9]. Furthermore, nanoparticles with unique properties have fluorescent image reconstruction and the activity of VCAM emerged as a promising class of molecule imaging agents. couldbedetectedthroughthesystem,whichshowedagreat Targeting moieties, therapeutic drug or gene, and different potential for the application in in vivo molecular imaging. imaging labels can be incorporated into nanoparticles to con- As this system could provide structural information while struct targeted imaging agents and multifunctional imaging keeping the merits of low cost of fluorescence imaging, it is agents which allow for multimodal imaging and theranostic worthy of promotion and application for the future. applications [58, 59]. Therefore, it can be seen that multimodality imaging is not a simple addition of various imaging technologies but 3.1. Targeted Molecular Imaging Agents Based on Small rather for producing synergistic effect. It can provide more Molecules. Small molecules, of which the size is usually less information to understand the biological processes compre- than 500 Da, are playing an important role in molecular hensively and objectively. But it is still difficult to carry out imaging. Due to their small size, small molecules have a wide multimodality imaging due to existing problems regarding range of application including intracellular and central ner- 18 the accuracy of coregistered image, extra ionizing radiation, vous system. F-FDG is the most widely used imaging agent the extra dosage of contrast agent, and the toxicity of fused based on small molecules, which is clinically applied for can- contrast agents. Therefore, it is in urgent need of developing cer imaging [60]. Ren et al. [61]reportedtheuseofgadolin- multimodality molecular imaging agent. ium (Gd) to label uniformly phosphorothioate-modified human tumor telomerase reverse transcriptase (hTERT) anti- 3. Imaging Agents sense oligonucleotide (ASON) targeting hTERT mRNA and conducted a study in BALB/c nude mice with 7.0T Micro- Molecular imaging depends greatly on the development of MRI, showing that Gd-DOTA-ASON was a potential intra- specific and sensitive imaging agents, which is a pivotal rate- cellular MR contrast probe for detection of telomerase- limiting step in the development of molecular imaging [8]. In positive carcinomas (Figure 6). a molecular imaging study, imaging agents are mainly used for interrogating or coupling back about a specific target of 3.2. Targeted Molecular Imaging Agents Based on Peptide. interest [10]. They usually consist of signal component and Peptide is an important class of ligand used for molecular targeting component. In recent years, the advancement of imaging [62]. Compared to small molecules, peptide has biochemistry has been achieved and the development of many advantages, such as superior selectivity and specificity molecular imaging technologies has led to the production of and easier modification without changing their binding a mass of molecular imaging agents [57]. A mass of targeting properties or distribution. Additionally, peptide is more sta- moieties, such as small molecule, peptide, antibody, and ble in atmospheric temperature than antibodies and has a aptamer, is applied to decorate ligand-directed (“targeted”) lower immunogenicity compared with antibodies. Recently, BioMed Research International 7

Before injection 0.5 h after injection 2 h after injection 6 h after injection

Gd-ASON

Gd-DTPA

Gd-SON

Figure 6: T1-weighted multiple slice multiple echo weighted MRI of nude mice bearing A549 tumors before and 0.5, 2, and 6 h after intraperitoneal injection. Tumors (arrows) all showed different enhancement level at 0.5 h, but in Gd-DOTA-ASON (upper line), the enhancement remained at 6 h, while Gd-DTPA (middle line) decreased obviously from 2 h (repetition time, 561 ms, echo time, 14 ms, and field of view, 4 cm); Gd-DOTA-SON (lower line) showed a similar trend to that of Gd-DOTA-ASON but with lower enhancement (adopted from Ren et al. [61]).

Hansen et al. [63]conjugatedapeptidewhichcouldbindto [68]. Because they enjoy a number of merits including high theurokinaseplasminogenactivatorreceptor(uPAR)with affinity and specificity, low immunogenicity, small size, stable high specificity and affinity to polyethylene glycol (PEG) structures, and ease of production, aptamers have recently coated USPIO nanoparticles. In vitro result showed that the attracted increasing attention [69, 70]. In recent years, probe peptide conjugated USPIO nanoparticles had a five times based on aptamer provides a new strategy for molecular higher uptake in a uPAR positive cell line compared to the imaging. Shi et al. [71]reportedtheuseofanactivatable nanoparticles with a nonspecific peptide. Hackel et al. [64] aptamerprobe(AAP)whichcouldbindmembraneproteins 18 used F labelled 2 cystine knot peptides and performed of living cancer cells with a high degree of specificity to micro-PET on BxPC3 pancreatic adenocarcinoma xenografts visualize the cancer inside mice. The results showed that in mice with them. Results indicated that these cystine knot the AAP could be used to specifically, quickly detect CCRF- peptide tracers had high tumor uptake, showing translational CEM cell in the serum or CCRF-CEM cell tumor in mice. promise for cancer imaging. Bagalkot et al. [72] recently described the use of a novel quantum dot conjugated with prostate specific membrane 3.3. Targeted Molecular Imaging Agents Based on Antibodies. antigen (PSMA) RNA aptamers to image and cure cancer. Characterized by the ability to bind their target with high Aptamer conjugated nanoparticles provide new strategy for specificity and affinity and easy synthesis, antibodies have targeted multimodality imaging. Hwang et al. [73] described a multimodal cancer-targeted imaging system for simultane- been applied for diagnosis and therapy [65]. So far, there ous fluorescence imaging, radionuclide imaging, and MRI in are more than eight FDA-approved radiolabeled antibodies vivo through an aptamer conjugated nanoparticle probes. The approved for SPECT molecular imaging and about twenty probe was synthesized by the AS1411 aptamer (MF-AS1411) antibodies approved for therapy. Recently, Zhang et al. [66] which targeted nucleolin a cobalt-ferrite nanoparticle com- reported the use of PET with (61/64) Cu-NOTA-TRC105- prised core of fluorescent rhodamine and a silica-based shell. Fab to image CD105 expression, which showed obvious and Thentheprobewasinjectedintravenouslyintonudemice target-specific uptake in the 4T1 tumorFigure ( 7). Abdolahi 67 bearing tumour xenografts and performed Ga radionuclide et al. [67] conjugated superparamagnetic iron oxide nanopar- imaging and MRI. The SPECT image showed that this probe ticles with an antibody which could bind to the extracellular exhibited a better accumulation in tumour 24 h after injection domain of PSMA and performed MRI with it. Results demon- thanthecontrolgroup.Furthermore,MRIimagesshowedthe strated that the nanoprobe could act as a specific MRI con- AS1411 conjugated nanoparticle as black signal in tumours trast agent for detection of PSMA-expressing prostate cancer 24 h after injection, while there were no T2 negative signals cells. in the control group. Finally, fluorescence images exhibited a higher signal in tumours of mice injected with aptamer 3.4. Targeted Molecular Imaging Agents Based on Aptamer. conjugated nanoparticles compared to the control one. Taken Aptamer, single-stranded DNA or RNA oligonucleotides, together, these results proved that aptamers can deliver the can bind to their target with high selectivity and specificity nanoparticlestotumortissue(Figure 8). 8 BioMed Research International

64 Cu-NOTA 7% ID/g TRC105-Fab

Blocking 0% ID/g

0.5 h 2 h 5 h 16 h 24 h 64 64 Figure 7: PET images were performed at 0.5, 2, 5, 16, and 24 h p.i. of Cu-NOTA-TRC105-Fab, or Cu-NOTA-TRC105-Fab after treatment with a 2 mg blocking dose of TRC105 before injection (adopted from Zhang et al. [66]).

MFR-AS1411 1 h 6 h 24 h ×104 2.0

1.5

1.0

0.5

(a1) (b1) (c1) (d1) MFR-AS1411mt ×104 2.0

1.5

1.0

0.5

(a2) (b2) (c2) (d2) Figure 8: Cancer-targeted multimodality imaging through MFRAS1411 conjugated nanoparticles. Tumor-bearing mice were intravenously injected with MFR-AS1411 nanoparticles (b1) and MFR-AS1411mt (b2) nanoparticles (control group). Radionuclide images were performed at 1, 6, and 24 h after injection. Scintigraphic images of tumors in mice injected with MFRAS1411 exhibited that MFR-AS1411 nanoparticles were accumulated in the tumors but MFRAS1411mt were not. Tumor growth patterns were followed using bioluminescence signals acquired from luciferase-expressing C6 cells (a1, a2). MR images of tumor-bearing mice before (c1, d1) and after (c2, d2) injection of MFR-AS1411 were obtained. Dark signal intensities at tumor sites were detected in MFR-AS1411-injected mice (arrowhead) (adopted from Hwang et al. [73]).

3.5. Multifunctional Molecular Imaging Agent. With multi- can be detected by different imaging modalities so as to modality imaging techniques clearly on the rise, the develop- boost the clinical benefits of multimodality imaging. Due ment over these new techniques has led to explosive growth in to their limited attachment points, small molecules are not multimodal imaging agent researches [74, 75]. Since different suitable for multimodality imaging. On contrast, nanoparti- imaging techniques can only detect their corresponding con- cles are attractive candidates for multimodal imaging probe trast agents, the patient who intends to perform multimodal- [76–78]. They possess high surface areas to volume ratio, ity imaging may need to inject different contrast mediums. which allows multiple modifications to ligands and different This will increase the patient’s economic burden and the imaging agents within the nanoparticles or on its surface. additional stress on the blood clearance mechanisms. More- Recently, John et al. [77]describedtheuseofatargetedmulti- over, it will expose him to side effect by the mutual inter- modal protein-shell microsphere which contained iron oxide ference between different contrast agents. Therefore, many nanoparticles in their cores and conjugated with the RGD researches are trying to design and develop a probe which peptide ligand to enhance the imaging ability of ultrasound, BioMed Research International 9

MRI and MM-OCT. Also, Liu et al. [79]designedaniron existing instrumentation and further efforts geared toward oxide nanoparticle-embedded polymeric microbubble used the combination of different modalities so as to make up for ultrasound imaging and MRI. Liang et al. [80]reported the disadvantages of different instruments. Multimodality the synthesis and evaluation of streptavidin nanoparticle- imaging has many advantages, but some problems still exist based complexes which were functionalized with biotinylated and need to be solved, such as the difficulty of designing a anti-Her2 Herceptin antibody as multimodality imaging PET/MRI system suited for the entire body, cost increase, agents to detect tumor in a model via both SPECT system and performance improvement, and multimodal contrast agent IVSI fluorescence camera. Willmann et al. [81] prepared a fusion. polymericcontrastagentMBQDs-PLGAsuitedforoptical Furthermore, as an emerging interdisciplinary science and ultrasonic molecular imaging. In addition, they used PET which brings together nuclear medicine, ultrasonic medicine, to assess in vivo whole-body biodistribution of microbub- radiology, pharmacy, and materials science, the development bles functionalized with anti-VEGFR2 antibodies that were of molecular imaging needs to strengthen interdisciplinary marked by the radiofluorination agent N-succinimidyl-4- 18 cooperation. Awareness of importance of multidisciplinary [ F] fluorobenzoate (SFB)82 [ ].Hence,itcanbeseenthat joint research should be strengthened. multimodal imaging agents are available, but their clinical The rapid expansion of molecular imaging application application still need further research. shows a promising prospect. Although overall the molecular Apart from imaging agent and ligands, therapeutic drug imaging is still at the initial stage of development, we believe or gene can also be incorporated in nanoparticles to construct that within the support and cooperation from imaging theragnostic agent which have an important role in therapy. experts and scholars, molecular imaging techniques would This agent enables observation of the extent of disease prior to eventually realize clinical transformation. therapeutic intervention. The ability to identify disease status andcontrolleddeliveryofdrugusingthesameagentwould help ensure that only potential responsive patients would Conflict of Interests be treated. Therefore, theragnostic agents show a promising prospectiveintherapy.Yanetal.[83]havesynthesizedanovel The authors declare no conflict of interests regarding the pub- targeted drug-loaded microbubble functionalized with LyP- lication of this paper. 1, a breast tumor homing peptide, and evaluated its effect in vivo. Results of the study demonstrated that the LyP- Acknowledgments 1-coated PTX-loaded microbubble improved the antitumor efficacymarkedlyandhadgreatpotentialinultrasound- This work was supported by National Natural Science Foun- assisted breast cancer treatment. dation of China (no. 81371572), Research Fund of Doctoral Program of Universities (no. 20124401120002), Sixth Spe- cial Project of China Postdoctoral Science Foundation (no. 4. Prospect 2013T60826), China Postdoctoral Science Foundation (no. 2011M501375), Research Project of Guangzhou Technology Molecular imaging technology truly enables dynamical, Bureau (no. 12C22021645), Research Project of Science and quantitative visualization of specific biochemical activity Technology Guangdong Province (no. 2012B050300026), without trauma in vivo at cellular and molecular level. It Research Project of Science and Technology Liwan Dis- has a direct impact on the modern and future medicine. In trict (no. 20124414124), and Natural Science Foundation of recent years, molecular imaging technology has seen certain Guangdong Province (no. S2012040006593). progresses in the early diagnosis, curative effect monitoring of diseases, drug development, gene therapy, and other fields, but some key problems regarding theory, technology, and sys- References tem, especially molecular imaging agents and imaging equip- ment, are not solved yet. The development of a new probe [1] D. Pan, G. M. Lanza, S. A. Wickline, and S. D. Caruthers, is not straightforward. Due to barriers in delivery, biological “Nanomedicine: perspective and promises with ligand-directed compatibility, and the diversity between species, there are molecular imaging,” European Journal of Radiology,vol.70,no. only a few of clinical molecular imaging agents available 2, pp. 274–285, 2009. currently. With the development of technology, it is expected [2] E. A. Osborn and F. A. Jaffer, “Advances in molecular imaging that more advancement will be achieved in the area of molec- of atherosclerotic vascular disease,” Current Opinion in Cardiol- ular imaging agent including targeted molecular imaging ogy,vol.23,no.6,pp.620–628,2008. agent and multifunctional molecular imaging agents. The [3] R. Weissleder and M. J. Pittet, “Imaging in the era of molecular application of nanoparticles has provided a platform for oncology,” Nature,vol.452,no.7187,pp.580–589,2008. theranostic researches. [4] R. Atreya and M. Goetz, “Molecular imaging in gastroenterol- Additionally, although a number of molecular imaging ogy,” Nature Reviews Gastroenterology & Hepatology,vol.10,no. instruments are available, all have their limitations. For 12, pp. 704–7712, 2013. instance,MRIisausefulclinicaldiagnostictool,butitsuf- [5] S. E. P. New and E. Aikawa, “Molecular imaging insights into fers from somewhat poor sensitivity. Therefore, more focus early inflammatory stages of arterial and aortic valve calcifica- shouldbeperformedonrefiningandimprovingupon tion,” Circulation Research, vol. 108, no. 11, pp. 1381–1391, 2011. 10 BioMed Research International

[6]C.M.Gomes,A.J.Abrunhosa,P.Ramos,andE.K.J.Pauwels, drug discovery and development,” Current Medicinal Chem- “Molecular imaging with SPECT as a tool for drug develop- istry, vol. 20, no. 3, pp. 378–388, 2013. ment,” Advanced Drug Delivery Reviews,vol.63,no.7,pp.547– [22] M. Benadiba, G. Luurtsema, and L. Wichert-Ana, “New molec- 554, 2011. ular targets for PET and SPECT imaging in neurodegenerative [7]A.T.Byrne,A.E.O’Connor,M.Halletal.,“Vascular-targeted diseases,” Revista Brasileira de Psiquiatria,vol.34,supplement photodynamic therapy with BF2-chelated tetraaryl-azadipyrro- 2, pp. S125–S148, 2012. methene agents: a multi-modality molecular imaging approach [23] N. M. Hijnen, A. de Vries, K. Nicolay, and H. Grull,¨ “Dual- to therapeutic assessment,” British Journal of Cancer,vol.101,no. isotope111In/177Lu SPECT imaging as a tool in molecular imag- 9, pp. 1565–1573, 2009. ing tracer design,” Contrast Media and Molecular Imaging,vol. [8]S.Luo,E.Zhang,Y.Su,T.Cheng,andC.Shi,“AreviewofNIR 7,no.2,pp.214–222,2012. dyes in cancer targeting and imaging,” Biomaterials,vol.32,no. [24] S. Hapdey, M. Soret, and I. Buvat, “Quantification in simultane- 29, pp. 7127–7138, 2011. ous 99mTc/123I brain SPECT using generalized spectral factor [9]M.L.JamesandS.S.Gambhir,“Amolecularimagingprimer: analysis: a Monte Carlo study,” Physics in Medicine and Biology, modalities, imaging agents, and applications,” Physiological vol.51,no.23,pp.6157–6171,2006. Reviews,vol.92,no.2,pp.897–965,2012. [25] A. M. Blamire, “The technology of MRI: the next 10 years?” [10] K. Chen and X. Chen, “Design and development of molecular British Journal of Radiology,vol.81,no.968,pp.601–617,2008. imaging probes,” Current Topics in Medicinal Chemistry,vol.10, [26] J. C. Gore, H. C. Manning, C. C. Quarles, K. W. Waddell, and no. 12, pp. 1227–1236, 2010. T. E. Yankeelov, “Magnetic resonance in the era of molecular [11] C. J. Anderson and R. Ferdani, “Copper-64 radiopharmaceu- imaging of cancer,” Magnetic Resonance Imaging,vol.29,no.5, ticals for PET imaging of cancer: advances in preclinical and pp. 587–600, 2011. clinical research,” Cancer Biotherapy and Radiopharmaceuticals, [27]P.L.Rapley,C.Witiw,K.Richetal.,“Invitromolecular vol. 24, no. 4, pp. 379–393, 2009. magnetic resonance imaging detection and measurement of apoptosis using superparamagnetic iron oxide + antibody as [12]J.Yuan,H.Zhang,H.Kauretal.,“Synthesisandcharacter- ligands for nucleosomes,” Physics in Medicine and Biology,vol. ization of theranostic poly(HPMA)-c(RGDyK)-DOTA-64Cu 57, no. 21, pp. 7015–7028, 2012. copolymer targeting tumor angiogenesis: tumor localization visualized by positron emission tomography,” Molecular Imag- [28] I. Debergh, N. Van Damme, D. De Naeyer et al., “Molecular ing,vol.12,no.3,pp.203–212,2012. imaging of tumor-associated angiogenesis using a novel mag- netic resonance imaging contrast agent targeting 𝛼v𝛽3inte- [13] C. Xavier, I. Vaneycken, M. D’huyvetter et al., “Synthesis, pre- grin,” Annals of Surgical Oncology,2013. clinical validation, dosimetry, and toxicity of 68Ga-NOTA- Anti-HER2 nanobodies for iPET imaging of HER2 receptor [29] S. Sawall, J. Kuntz, M. Socher et al., “Imaging of cardiac per- expression in cancer,” The Journal of Nuclear Medicine,vol.54, fusion of free-breathing small animals using dynamic phase- no. 5, pp. 776–784, 2013. correlated micro-CT,” ,vol.39,no.12,pp.7499– 7506, 2012. [14] M. E. Phelps, “Positron emission tomography provides molecu- [30]S.M.Johnston,G.A.Johnson,andC.T.Badea,“Temporaland lar imaging of biological processes,” Proceedings of the National spectral imaging with micro-CT,” Medical Physics,vol.39,no.8, Academy of Sciences of the United States of America,vol.97,no. pp. 4943–4958, 2012. 16, pp. 9226–9233, 2000. [31]J.Schaap,J.A.deGroot,K.Niemanetal.,“Hybridmyocardial [15] A. Afshar-Oromieh, U. Haberkorn, M. Eder, M. Eisenhut, and perfusion SPECT/CT coronary and invasive coro- C. Zechmann, “PET imaging with a [68Ga]gallium-labelled nary angiography in patients with stable angina pectoris lead to PSMA ligand for the diagnosis of prostate cancer: biodis- similar treatment decisions,” Heart,vol.99,no.3,pp.188–194, tribution in humans and first evaluation of tumour lesions,” 2013. European Journal of Nuclear Medicine and Molecular Imaging, vol.40,no.4,pp.486–495,2013. [32]R.Popovtzer,A.Agrawal,N.A.Kotovetal.,“Targetedgold nanoparticles enable molecular CT imaging of cancer,” Nano [16] A.J.Beer,H.Kessler,H.J.Westeretal.,“PETimagingofintegrin Letters,vol.8,no.12,pp.4593–4596,2008. 𝛼3𝛽v expression,” Theranosttiics, vol. 1, pp. 48–57, 2011. [33] F. Hyafil, J.-C. Cornily, J. E. Feig et al., “Noninvasive detection of [17] B. J. Pichler, M. S. Judenhofer, and C. Pfannenberg, “Multi- macrophages using a nanoparticulate contrast agent for com- modal imaging approaches: PET/CT and PET/MRI—part 1,” puted tomography,” Nature Medicine,vol.13,no.5,pp.636–641, Handbook of Experimental Pharmacology,no.185,pp.109–132, 2007. 2008. [34] D. Pan, T. A. Williams, A. Senpan et al., “Detecting vascular [18] D. BelkicandK.Belki´ c,´ “Molecular imaging in the framework biosignatures with a colloidal, radio-opaque polymeric nano- of personalized cancer medicine,” The Israel Medical Association particle,” Journal of the American Chemical Society,vol.131,no. Journal,vol.15,pp.665–672,2013. 42, pp. 15522–15527, 2009. [19]W.P.Andrade,E.N.Lima,C.A.Osorio´ et al., “Can FDG-PET/ [35]J.Li,A.Chaudhary,S.J.Chmuraetal.,“AnovelfunctionalCT CT predict early response to neoadjuvant chemotherapy in contrast agent for molecular imaging of cancer,” Physics in Med- breast cancer?” European Journal of Surgical Oncology,vol.39, icine and Biology,vol.55,no.15,pp.4389–4397,2010. no. 12, pp. 1358–1363, 2013. [36] M. Rotman, T. J. A. Snoeks, and L. van der Weerd, “Pre-clinical [20] P. Blake, B. Johnson, and J. W. VanMeter, “Positron emission optical imaging and MRI for drug development in Alzheimer’s tomography (PET) and single photon emission computed disease,” Drug Discovery Today,vol.8,no.2–4,pp.e117–e125, tomography (SPECT): clinical applications,” JournalofNeuro- 2011. Ophthalmology,vol.23,no.1,pp.34–41,2003. [37] L. E. Edgington, A. B. Berger, G. Blum et al., “Noninvasive opti- [21] A. M. Catafau and S. Bullich, “Molecular imaging PET and cal imaging of apoptosis by caspase-targeted activity-based SPECT approaches for improving productivity of antipsychotic probes,” Nature Medicine,vol.15,no.8,pp.967–973,2009. BioMed Research International 11

[38] G. Niu, L. Zhu, D. N. Ho et al., “Longitudinal bioluminescence [55] A. Kjær, A. Loft, I. Law et al., “PET/MRI in cancer patients: first imaging of the dynamics of Doxorubicin induced apoptosis,” experiences and vision from Copenhagen,” Magnetic Resonance Theranostics,vol.3,no.3,pp.190–200,2013. MaterialsinPhysics,BiologyandMedicine,vol.26,no.1,pp.37– [39] R. Atreya, M. J. Waldner, and M. F. Neurath, “Molecular imag- 47, 2012. ing: interaction between basic and clinical science,” Gastroen- [56]B.Li,M.Abran,C.Matteau-Pelletieretal.,“Low-costthree- terology Clinics of North America,vol.39,no.4,pp.911–922, dimensional imaging system combining fluorescence and ultra- 2010. sound,” Journal of Biomedical Optics,vol.16,no.12,ArticleID [40]J.Bzyl,W.Lederle,M.Palmowski,andF.Kiessling,“Molecular 126010, 2011. and functional ultrasound imaging of breast tumors,” European [57] P. Agrawal, G. J. Strijkers, and K. Nicolay, “Chitosan-based sys- Journal of Radiology, vol. 81, supplement 1, pp. S11–S12, 2012. tems for molecular imaging,” Advanced Drug Delivery Reviews, [41] N. Deshpande, A. Needles, and J. K. Willmann, “Molecular vol.62,no.1,pp.42–58,2010. ultrasound imaging: current status and future directions,” [58]M.A.McDonald,P.C.Wang,andE.L.Siegel,“Proteinnano- Clinical Radiology,vol.65,no.7,pp.567–581,2010. spheres: synergistic nanoplatform-based probes for multimo- [42] P.Li, Y. Zheng, H. Ran et al., “Ultrasound triggered drug release dality imaging,” in Reporters, Markers, Dyes, Nanoparticles, and from 10-hydroxycamptothecin-loaded phospholipid microbub- Molecular Probes for Biomedical Applications III, Proceedings of bles for targeted tumor therapy in mice,” Journal of Controlled SPIE, San Francisco, Calif, USA, January 2011. Release,vol.162,no.2,pp.349–354,2012. [59]G.D.Kenny,N.Kamaly,T.L.Kalberetal.,“Novelmultifunc- [43]J.T.Sutton,K.J.Haworth,G.Pyne-Geithman,andC.K.Hol- tional nanoparticle mediates siRNA tumour delivery, visuali- land, “Ultrasound-mediated drug delivery for cardiovascular sation and therapeutic tumour reduction in vivo,” Journal of disease,” ExpertOpiniononDrugDelivery,vol.10,no.5,pp.573– Controlled Release, vol. 149, no. 2, pp. 111–116, 2011. 592, 2013. [60] L. Evangelista, A. R. Cervino, S. Chondrogiannis et al., “Com- [44]M.Mancini,A.Greco,G.Salvatoreetal.,“Imagingofthyroid parison between anatomical cross-sectional imaging and 18F- tumor angiogenesis with microbubbles targeted to vascular FDG PET/CT in the staging, restaging, treatment response, and endothelial growth factor receptor type 2 in mice,” BMC Medical long-term surveillance of squamous cell head and neck cancer: Imaging, vol. 13, article 31, 2013. a systematic literature overview,” Nuclear Medicine Communi- [45] P.Li, Y. Zheng, H. Ran et al., “Ultrasound triggered drug release cations,vol.35,no.2,pp.123–134,2014. from 10-hydroxycamptothecin-loaded phospholipid microbub- [61] B. X. Ren, F. Yang, G. H. Zhu et al., “Magnetic resonance tumor bles for targeted tumor therapy in mice,” Journal of Controlled targeting imaging using gadolinium labeled human telomerase Release,vol.162,no.2,pp.349–354,2012. reverse transcriptase antisense probes,” Cancer Science,vol.103, [46] Z.-Y. Chen, K. Liang, and R. X. Qiu, “Targeted gene delivery no. 8, pp. 1434–1439, 2012. in tumor xenografts by the combination of ultrasound-targeted [62] J. Gao and H. Zheng, “Illuminating the lipidome to advance microbubble destruction and polyethylenimine to inhibit sur- biomedical research: peptide-based probes of membrane lipids,” vivin gene expression and induce apoptosis,” Journal of Experi- Future Medicinal Chemistry,vol.5,no.8,pp.947–959,2013. mental and Clinical Cancer Research,vol.29,no.1,pp.1–9,2010. [63] L. Hansen, E. K. Unmack Larsen, E. H. Nielsen et al., “Targeting [47] W. Cai and X. Chen, “Nanoplatforms for targeted molecular of peptide conjugated magnetic nanoparticles to urokinase plas- imaging in living subjects,” Small,vol.3,no.11,pp.1840–1854, minogen activator receptor (uPAR) expressing cells,” Nanoscale, 2007. vol. 5, no. 17, pp. 8192–8201, 2013. [48] Y. Lin, Z. Y. Chen, and F. Yang, “Ultrasound-based multimodal [64] B. J. Hackel, R. H. Kimura, and Z. Miao, “18F-Fluorobenzoate- molecular imaging and functional ultrasound contrast agents,” labeled cystine knot peptides for PET imaging of integrin 𝛼v𝛽6,” Current Pharmaceutical Design,vol.19,no.18,pp.3342–3351, Nanoscale,vol.55,no.7,pp.1101–1105,2013. 2013. [65]S.Oliveira,R.Heukers,J.Sornkom,R.J.Kok,andP.M.van [49]T.D.Poeppel,B.J.Krause,T.A.Heusner,C.Boy,A.Bockisch, Bergen en Henegouwen, “Targeting tumors with nanobodies and G. Antoch, “PET/CT for the staging and follow-up of for cancer imaging and therapy,” Journal of Controlled Release, patients with malignancies,” EuropeanJournalofRadiology,vol. vol. 172, no. 3, pp. 607–617, 2013. 70,no.3,pp.382–392,2009. [66] Y. Zhang, H. Hong, and H. Orbay, “PET imaging of CD105/ [50] W. Cai, G. Niu, and X. Chen, “Multimodality imaging of the 61/64 HER-kinase axis in cancer,” European Journal of Nuclear Medi- endoglin expression with a Cu-labeled Fab antibody frag- cine and Molecular Imaging,vol.35,no.1,pp.186–208,2008. ment,” European Journal of Nuclear Medicine and Molecular [51] W. Cai and X. Chen, “Multimodality molecular imaging of Imaging,vol.40,no.5,pp.759–767,2013. tumor angiogenesis,” The Journal of Nuclear Medicine,vol.49, [67] M. Abdolahi, D. Shahbazi-Gahrouei, S. Laurent et al., “Synthesis supplement 2, pp. 113S–128S, 2008. and in vitro evaluation of MR molecular imaging probes using [52] Z. S. Browning, A. A. Wilkes, D. S. Mackenzie et al., “Using PET/ J591 mAb-conjugated SPIONs for specific detection of prostate CT imaging to characterize 18 F-fluorodeoxyglucose utilization cancer,” Contrast Media & Molecular Imaging,vol.8,no.2,pp. in fish,” JournalofFishDiseases,vol.36,no.11,pp.911–919,2013. 175–184, 2013. [53] R. Abgral, S. Querellou, G. Potard et al., “Does 18F-FDG PET/ [68] P.R.Bouchard,R.M.Hutabarat,andK.M.Thompson,“Discov- CT improve the detection of posttreatment recurrence of head ery and development of therapeutic aptamers,” Annual Review and neck squamous cell carcinoma in patients negative for dis- of Pharmacology and Toxicology,vol.50,pp.237–257,2010. ease on clinical follow-up?” Journal of Nuclear Medicine,vol.50, [69] A. D. Keefe, S. Pai, and A. Ellington, “Aptamers as therapeutics,” no. 1, pp. 24–29, 2009. Nature Reviews Drug Discovery,vol.9,no.7,pp.537–550,2010. [54] W. W. Lee, B. Marinelli, A. M. Van Der Laan et al. et al., “PET/ [70] H. Hong, S. Goel, Y. Zhang, and W. Cai, “Molecular imaging MRI of inflammation in myocardial infarction,” Journal of the with nucleic acid aptamers,” Current Medicinal Chemistry,vol. American College of Cardiology,vol.59,no.2,pp.153–163,2012. 18,no.27,pp.4195–4205,2011. 12 BioMed Research International

[71] H. Shi, X. He, K. Wang et al., “Activatable aptamer probe for contrast-enhanced in vivo cancer imaging based on cell mem- brane protein-triggered conformation alteration,” Proceedings of the National Academy of Sciences of the United States of America,vol.108,no.10,pp.3900–3905,2011. [72]V.Bagalkot,L.Zhang,E.Levy-Nissenbaumetal.,“Quantum dot-aptamer conjugates for synchronous cancer imaging, ther- apy, and sensing of drug delivery based on Bi-fluorescence resonance energy transfer,” Nano Letters,vol.7,no.10,pp.3065– 3070, 2007. [73] D. W. Hwang, H. Y. Ko, J. H. Lee et al., “A nucleolin-targeted multimodal nanoparticle imaging probe for tracking cancer cells using an aptamer,” Journal of Nuclear Medicine,vol.51,no. 1, pp. 98–105, 2010. [74] A. Louie, “Multimodality imaging probes: design and chal- lenges,” Chemical Reviews,vol.110,no.5,pp.3146–3195,2010. [75] M. A. Hall, S. Kwon, H. Robinson et al., “Imaging prostate cancer lymph node metastases with a multimodality contrast agent,” Prostate,vol.72,no.2,pp.129–146,2012. [76] S. Y. Madani, F. Shabani, M. V. Dwek et al., “Conjugation of quantumdotsoncarbonnanotubesformedicaldiagnosisand treatment,” International Journal of Nanomedicine,vol.8,pp. 941–950, 2013. [77]R.John,F.T.Nguyen,K.J.Kolbecketal.,“Targetedmultifunc- tional multimodal protein-shell microspheres as cancer imag- ing contrast agents,” Molecular Imaging and Biology,vol.14,pp. 17–24, 2012. [78] J. Ma, P. Huang, M. He et al., “Folic acid-conjugated LaF3:Yb,Tm@SiO2 nanoprobes for targeting dual-modality imaging of upconversion luminescence and X-ray computed tomography,” TheJournalofPhysicalChemistryB,vol.116,no. 48, pp. 14062–14070, 2012. [79] Z. Liu, T. Lammers, J. Ehling et al., “Iron oxide nanoparticle- containing microbubble composites as contrast agents for MR and ultrasound dual-modality imaging,” Biomaterials,vol.32, no.26,pp.6155–6163,2011. [80] M. Liang, X. Liu, D. Cheng et al., “Multimodality nuclear and fluorescence tumor imaging in mice using a streptavidin nano- particle,” Bioconjugate Chemistry,vol.21,no.7,pp.1385–1388, 2010. [81] J. K. Willmann, Z. Cheng, C. Davis et al., “Targeted microbub- bles for imaging tumor angiogenesis: assessment of whole-body biodistribution with dynamic micro-pet in mice,” Radiology, vol. 249, no. 1, pp. 212–219, 2008. [82] N. Deshpande, A. Needles, and J. K. Willmann, “Molecular ultrasound imaging: current status and future directions,” Clinical Radiology,vol.65,no.7,pp.567–581,2010. [83] F. Yan, X. Li, Q. Jin et al., “Therapeutic ultrasonic microbubbles carrying paclitaxel and LyP-1 peptide: preparation, characteri- zation and application to ultrasound-assisted chemotherapy in breast cancer cells,” Ultrasound in Medicine and Biology,vol.37, no. 5, pp. 768–779, 2011. M EDIATORSof INFLAMMATION

The Scientific Gastroenterology Journal of Research and Practice Diabetes Research Disease Markers World Journal Hindawi Publishing Corporation Hindawi Publishing Corporation Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Hindawi Publishing Corporation Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014

Journal of International Journal of Immunology Research Endocrinology Hindawi Publishing Corporation Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014

Submit your manuscripts at http://www.hindawi.com

BioMed PPAR Research Research International Hindawi Publishing Corporation Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014

Journal of Obesity

Evidence-Based Journal of Stem Cells Complementary and Journal of Ophthalmology International Alternative Medicine Oncology Hindawi Publishing Corporation Hindawi Publishing Corporation Hindawi Publishing Corporation Hindawi Publishing Corporation Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014

Parkinson’s Disease

Computational and Mathematical Methods Behavioural AIDS Oxidative Medicine and in Medicine Neurology Research and Treatment Cellular Longevity Hindawi Publishing Corporation Hindawi Publishing Corporation Hindawi Publishing Corporation Hindawi Publishing Corporation Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014